Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
using P = pair<int, int>;

const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { 1, 0, -1, 0 };

int main()
{
	int H, W;
	cin >> H >> W;
	vector<string> S(H);
	for (int i = 0; i < H; i++) {
		cin >> S[i];
	}
	int res = 0;
	for (int i = 0; i < H; i++) {
		for (int j = 0; j < W; j++) {
			res += S[i][j] != '#';
		}
	}
	int si = 0, sj = 0;
	queue<P> q;
	vector<vector<int>> d(H, vector<int>(W, -1));
	q.emplace(si, sj);
	d[si][sj] = 1;
	while (!q.empty()) {
		P p = q.front(); q.pop();
		for (int i = 0; i < 4; i++) {
			int tx = p.first + dx[i], ty = p.second + dy[i];
			if (0 <= tx && tx < H && 0 <= ty && ty < W && S[tx][ty] == '.' && d[tx][ty] == -1) {
				d[tx][ty] = d[p.first][p.second] + 1;
				q.emplace(tx, ty);
			}
		}
	}
	cout << (d[H - 1][W - 1] == -1 ? -1 : res - d[H - 1][W - 1]) << endl;
	return 0;
}